In original Vex Thal (Shadows of Luclin) at -455, 1400, 0, which is on the first floor, southern path, in a small hallway just west of the DXX area. There is a robed shade mob outside the zone boundary, standing on the wrong side of the hallway wall. You can just barely see his name peeking out of the wall at some angles. One way to aggro this mob is to send your pet after it. This occurs in both regular zone VT and instance zone VT via Agent of Change. This misplaced mob has been there every time I've gone to VT, so far as I remember. I checked other hallways with similar geometry and don't see any others. Just the one. And this mob does not have the same name every time, might start with Zun or Qua or possibly other trash mob names.
I remember this mob! From all the way back to the original Vex Thal. It has been stuck behind that wall forever, partially visible through that 'window', or if you max shrink and look through the wall. It has been there forever, and I remember using the /bug feature in game reporting it with target info. Many years ago. Will it finally be fixed in 2022?
